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Discussion Starter · #1 ·
Well, this code has been popping up for the past three months off and on, but this time as soon as I cleared it then it would come back within a few miles of driving. Before it would take a month or so.

So took it in to the dealer and this is what they found and was written on the work order.

"Customer states the check engine light is on. Tech inspected the vehicle and recovered the DTC P0171, Tech duplicated & performed diag, Tech found the intake manifold tuning valve was broken and causing the engine to run lean, Tech also states the PCV tube was cracked allowing unmetered air to enter the engine. Tech replaced the intake manifold and the PCV tube then cleared the codes and test drove the vehicle to verify the repair was complete and the concern was resolved."

Well, all was well, it took them all day to do the repair and we picked it up after the service department went home due to traffic getting to the dealership was a major PITA. We no sooner drove off the lot and went about a 1/4 mile and the light came back on. Contacted OnStar and it is the same code. So I'm wondering if they didn't tighten something or this now might be the valve cover. I'm going to call them first thing tomorrow morning when they open and see what is up. This of course is an hour and a half away from me in the town where my daughter is going to college. So she will have to take in in and drop it off by herself this time. At least she knows what to do since I had her do it today with me being there showing her what she needed to do. I'm hoping it is a simple issue, I guess we will see.
 

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Just for kicks and grins, check to see that the oil cap and dipstick are seated properly. I'm not sure what would happen if they were loose, but it's worth checking.

What size engine is this? I thought manifold tuning valves were only on the 1.8.
 

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Discussion Starter · #3 ·
Just for kicks and grins, check to see that the oil cap and dipstick are seated properly. I'm not sure what would happen if they were loose, but it's worth checking.
I will have her check that out. It was dark I needed to get home so we went and grabbed a quick dinner.
 

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I'm not sure if you saw my edit asking about the engine size.
 

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Discussion Starter · #6 ·
Back to the dealer today for the same code coming back. This time they said that the Valve cover was bad. It showed good when they were in there to replace the intake and PCV tube.
Hopefully this takes care of it. From what I have read for the most part the most common fix for the P0171 code is the valve cover. I didn't see anything in all my searches that pointed to an intake manifold tuning valve.

Just glad it was take care of under warranty.
 

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Just for kicks and grins, check to see that the oil cap and dipstick are seated properly. I'm not sure what would happen if they were loose, but it's worth checking.

What size engine is this? I thought manifold tuning valves were only on the 1.8.
The 1.8's have a valve that maintains air velocity built into the manifold.....when it fails, the manifold requires replacement.

The 1.4t's have a vacuum check valve built into the manifold....when it sticks closed, the manifold requires replacement.
As the OP has learned, when the check valve sticks, the PCV, more often than not, ends up damaged as well because it has experienced vacuum loads far higher than it was designed for.

Rob
 

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Yeah, my intake check valve went bad and took out the valve cover that had JUST been replaced 3 months earlier.
 

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The 1.8's have a valve that maintains air velocity built into the manifold.....when it fails, the manifold requires replacement.

The 1.4t's have a vacuum check valve built into the manifold....when it sticks closed, the manifold requires replacement.
As the OP has learned, when the check valve sticks, the PCV, more often than not, ends up damaged as well because it has experienced vacuum loads far higher than it was designed for.
Agreed. But OP says he has a 1.4T and the tech told him he had a bad "manifold tuning valve". :signs053:

Maybe the tech meant vacuum check valve, or something got lost in the telling. I just get an uneasy feeling when a repair place uses the wrong name for parts.
 

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Agreed. But OP says he has a 1.4T and the tech told him he had a bad "manifold tuning valve". :signs053:

Maybe the tech meant vacuum check valve, or something got lost in the telling. I just get an uneasy feeling when a repair place uses the wrong name for parts.
Seriously though. If they're not even using the correct words, there's no telling what else they might be doing wrong.
 

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I'll be devils advocate and suggest that, to the tech., a valve is a valve.....a part in the manifold that isn't serviceable.

And, of course, the tech. told the writer what failed.....the writer 'may' have interpeted and relayed foggy information.....

Rob
 
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